1. Field of Invention
The present invention relates to a kinase which is activated by transforming growth factory-.beta. (TGF-.beta.) and functions in the TGF-.beta. family signal transduction system (transforming growth factor-activated kinase: TAK1), to a process for production thereof, and to a gene coding for it. TAK1, also known as an activator of MAPK kinase (AMK-1), is an enzyme (a kinase) which is activated by TGF-.beta. and BMP (bone morphogenetic protein) and in turn activates MAPK kinase by phosphorylation.
2. Related Art
The receptors of TGF-.beta. superfamily comprise Ser/Thr kinases in the cytoplasmic region, and are classified into type I which has a repeating sequence of Gly-Ser (GS box) at the amino terminal proximal to the transmembrane domain, and type II which does not have the GS box. It is believed that, in the case of TGF-.beta., ligands form complexes with type I receptors after binding to type II receptors, and the kinases constitutively active type II receptors phosphorylate the type I receptors in the vicinity of the GS box, thus activating the type I receptors for transduce the signal from those ligands into the cell. However, virtually nothing is known about the signal-transducing molecules downstream from these receptors.
According to the known signal transducing cascade from extracellular mating pheromones to mating in the eukaryotic budding yeast Saccharomyces cerevisiae, G protein is activated by the mating pheromone, G protein activates MAPKK kinase (MAPKKK) (Ste11), the activated MAPKKK activates MAPK kinase (MAPKK) by phosphorylation, the thus activated MAPKK (Ste7) in turn activates MAP kinase (mitogen-activated protein kinase: MAPK) by phosphorylation, and finally MAPK activates FUSI protein, which initiates mating of the cells.